When British colonial rulers hastily left South Asia at Pakistan's painful birth in 1947, the ensuing chaos and violence meant little attention was paid to the architecture they built or influenced in Pakistan's biggest city, Karachi. More than 70 years later, architectural gems have been torn down and many are either crumbling or under threat from real estate developers in Pakistan's commercial capital which is mushrooming into a mega-city. The structures, weathered by the salty air, open the door to Karachi's difficult past, researchers say, pointing out that many of the original owners were among millions of Muslim and Hindu refugees who fled their homes amid communal and religious violence that accompanied the end of colonial rule in India in 1947 and the creation of Pakistan. REUTERS/Akhtar Soomro SEARCH "SOOMRO ARCHITECTURE" FOR THIS STORY. SEARCH "WIDER IMAGE" FOR ALL STORIES.